Meeting the medical disposables challenge

There are many things to take into consideration when designing medical disposable devices—particularly if they are for use outside the hospital or care provider’s office—such as ease of use, safety, and cost.

Home care is becoming more predominant as hospital stays become shorter—even for some of the most serious surgeries—as insurers have reduced allowances for stays and payments to hospitals. With healthcare costs again in the spotlight, cost cutting is pervasive, to include in the disposable medical products arena.

Hitting goals for low production costs often requires a new way of looking at these single-use devices (SUDs) and designing for manufacturability and reduced material usage on the processing side, while considering ease-of-use and minimizing the potential for error on the patient side. Many of the same considerations that are critical in designing multiple-use medical devices are also major considerations for SUDs.

Tom O’Brien, product marketing manager for Lexan and Cycoloy and healthcare industry manager for the Performance Products unit at supplier Sabic Innovative Plastics (Pittsfield, MA), says that one of the trends in healthcare is increasing the throughput of patients in the system. “The longer you’re in an operating room, the longer you’re being treated, the more it costs, and insurance companies are paying less,” says O’Brien. “In the area of disposables, we’re seeing certain surgical instruments that have historically been fabricated of metal going to plastic so they can be disposable. It eliminates the sterilization process, and allows the surgeon to move right on to the next surgery with no delays.”

In one case, O’Brien explains, Sabic worked with an OEM on a metal skin stapler. “This skin stapler had between 20 and 25 components, so after each surgery the entire device had to be completely disassembled, sterilized, and put it back together,” he says. “There was a tendency to lose parts, and there was the time it takes in the sterilizer. Today, they use a disposable skin stapler.”

Dave Devito, product marketing manager for Sabic’s LNP compounds product line and healthcare industry manager for specialty products, says that the term “disposable” spans a wide range of products. “Disposable might be an $800 skin stapler or a $20 syringe. I do know the medical device companies are investing in new products all the time, but always watching their costs,” Devito says. “Major device manufacturers are definitely expanding more into disposables, with combined functionality designed into the product. They are coming out with new products—doing some innovation. Minimally invasive surgical devices are expanding for more in-and-out procedures.”

Kevin Dunay, market segment leader, medical polycarbonates NAFTA for Bayer MaterialScience LLC (Pittsburgh, PA), sees device companies asking for materials allowing for longer flow lengths in multi-cavity molds. Reducing costs to manufacture also means designing for thinner wall sections as well. “We see a growing trend in the health care market for thin-wall applications,” Dunay says.

To address the demand for these, his company in June launched its Makrolon Rx2435 polycarbonate. Like its predecessor, Makrolon Rx2530, Makrolon Rx2435 resin exhibits a good balance of mechanical strength and toughness, but the new grade also adds easier flow, specifically to meet the needs of thin-wall applications. Potential thin-wall applications for Makrolon Rx2435 include dialysis components, catheter connectors, surgical instruments—such as tracers, retractors and handles—and drug delivery devices, he adds.

Dunay notes that SUD makers continue to look at both new devices and “next-gen” products. “Certainly it’s easier for the OEMs to make small changes to a device they have a history with,” he states. “They are continuing to look at new technology, but they want to be cautious, too, because they need a high degree of safety and reliability.”

Sabic’s O’Brien explains that the OEM typically works with the end user as they’re designing new products. “The surgeons want the feel—especially when an instrument goes from metal to plastic—that it’s sturdy and that it feels right in their hands. They need the instrument or device to work the same way each time.”

O’Brien says that in light of the economy, new designs get put on hold more than they used to. Also, approval time for new designs can take a long time. “It might be more cost-effective to tweak a design on something that’s already proven as it’s easier for them to launch a redesign than come out with a whole new product,” he says.    

Single versus multiple use
If medical device OEMs move increasingly toward SUDs—even in surgical instruments—has the need for sterilization waned? Sabic’s Devito says it’s not necessarily the case. “It’s still critical in application development to look at sterilization requirements, and it’s one of the main questions asked in the development process,” he says. “I think it’s all about efficiency. And it’s still one of the main CTQ (critical to quality) issues when device makers promote their products in healthcare.”

Bayer’s Rx2435 grade also addresses the increasing demand for a radiation-stabilized medical grade of polycarbonate. It is gamma-stabilized and typically offered in the color Gamma (color code 451118), but can also be colored in any of the company’s other Rx Medical colors, all of which meet the requirements of FDA-Modified ISO 10993, Part1 tests with human tissue contact time of 30 days or less. Sabic’s portfolio includes materials that can meet every type of sterilization requirement including gamma and steam autoclave, which are the primary methods, notes O’Brien. “With gamma you have color shift, but our products have color stabilizer in them so when PC devices are gamma sterilized they don’t shift toward yellow as much. It will shift a bit, then go back to clear. A lot of disposables are gamma sterilized because it’s quick.”

With steam autoclave sterilization, there are two temperatures used, 134ºC or 121ºC. “Hospitals prefer the 134ºC because it’s quicker. You’re talking more robust materials for that, so it’s a trade-off. A lot of disposables like Y-sites, stopcocks, are PC that is generally gamma sterilized at the OEM, used once, and tossed. It all depends on the type of sterilization method,” says O’Brien.
O’Brien is confident about the strength of the SUD market, but with reservations. “I think we’re seeing more applications and new products, but we’ve also seen that healthcare isn’t recession proof,” he says. “We’ve seen budget cuts in hospitals, OEMs moving a bit slower on new products than they used to. It’s still a good market, but they look at costs a lot more closely than they used to and ask that big question: What can I do to take costs out? —Clare Goldsberry

ISO certification opens medical doors
Mack Prototype Inc. (Gardner, MA), a division of custom injection molder Mack Molding Co. and specializing in SLA rapid prototyping, CNC machining, and injection molding (8 presses sized 10-230 tons) for low-volume, small-to-medium parts processing, recently received its ISO 13485 certification, the international quality standard for medical device manufacturing. “Achieving this quality hallmark uniquely positions us as a prototype house and low-volume manufacturer, as many manufacturers our size are not certified to this stringent medical standard,” says Rick Perry, president of Mack Prototype. “It will put us at the table with major medical OEMs, who require suppliers to be certified to ISO 13485 in order to quote new projects. And based on customer needs, it will allow us to partner with Mack Molding, which is FDA registered and has been certified to ISO 13485 for several years, to provide a low-volume solution for major medical OEMs.”

Michael Hanson, senior technical development engineer at the processor, explains that when designing medical disposables, it’s important to start with a target cost, which narrows the scope of possibilities. “Another often overlooked step is to clearly define that part’s requirements,” Hanson says. “The overall goal is to meet the part requirements at the lowest possible cost, so this is where you must start.” Other design considerations he mentions include avoiding sharp edges that could easily prick surgical gloves; avoiding thin and thick sections to minimize molded-in stress levels and part warpage, and, of course, choosing the correct resin. —Clare Goldsberry


Medical applications: pick your plastic
Resin selection of course is not as simple a matter as that, and Hanson offers some questions that can help guide a part designer's down the path to the right material for a medical device. These include:

• How will the part be sterilized: ETO, E-Beam, Gamma radiation—and what is the radiation dose?
• How will the part be used? Will it interface with other surgical instruments?
• Will the part be exposed to a sterilizing solution with ultrasonic cleaning action?
• How will the part be marked for traceability? Pad printing, laser marking, inmold marking?
• Is color important? Will the part be clear, translucent, or opaque?
• Does it require soft-touch for grip?
• Does it come in contact with any other substance or solution?
• What are the strength requirements?

In general, says Hanson, amorphous resins are preferred over semi-crystalline resins for radiation sterilization applications. If a semi-crystalline resin is chosen, then the lower the crystallinity, the better. The highest molecular-weight resin with the narrowest molecular-weight distribution works best. —Clare Goldsberry